Nowadays sensor lights or switches use infrared detectors, microwave devices or ultrasonic transceivers which detect motion of objects to accomplish the control of sensor lights or switches. The infrared detectors or microwave devices with the merits of easy-design and low-cost may only provide a function of on/off control. However, the ultrasonic transceivers may not only provide the function of on/off control but also provide a function of displacement measurement. The relative distance between the object and the ultrasonic transceiver are calculated based on the speed of the ultrasound travelling in the corresponding medium and the time-of-flight (TOF) of the ultrasound. Thus, the ultrasonic transceivers are widely applied in motion/displacement detection of the objects.
U.S. Pat. No. 4,305,021 discloses a switch for controlling the operation of a light source in response to the presence of a moving person or object which is detected by a microwave device and in response to the magnitude of ambient light provided other than by the light source.
U.S. Pat. No. 4,551,654 discloses a lighting control circuit responsive to amplitude variations related to the effects of movement on the reflection of electromagnetic energy at an ultrasonic frequency. U.S. Pat. No. 7,027,355 discloses an ultrasonic device which is provided for detecting motion or displacement of an object in a monitored zone.
In conclusion, the ultrasonic transceivers are applied for on/off control or displacement calculation of the detected object. The detailed structure and basic principle of the ultrasonic transceivers are described in detail below.
Refer to FIG. 1, which illustrates the circuit structure of an ultrasonic device applied as a switch. Wherein a transmitter circuit 11 and a receiver circuit 12 are positioned in opposition. The receiver circuit 12 receives an ultrasonic signal transmitted by the transmitter circuit 11 when there's no obstacle 13 while the receiver circuit 12 doesn't receive the ultrasonic signal transmitted by the transmitter circuit 11 when there's an obstacle 13. That is to say, the detected voltage level by the receiver circuit 12 is varied when there's an obstacle 13 in the detected range of the receiver circuit 12. Thus, nowadays outdoor motion sensor security lights usually adopt the similar circuit structure of the ultrasonic device mentioned above.
Refer to FIG. 2, which illustrates the circuit structure of an ultrasonic device applied for displacement calculation. Wherein a transmitter circuit 21 and a receiver circuit 22 are positioned on the same side. The ultrasonic signal transmitted by the transmitter circuit 21 is reflected to the receiver circuit 22 by an obstacle 23. The displacement is then calculated based on the speed of the ultrasonic signal travelling in the corresponding medium and the time-of-flight (TOF) of the ultrasonic signal. The medium is not limited to air. The medium may also be liquid or solid. Representative application of ultrasonic displacement calculation is water depth detection or water level detection and so on.
The prior art of the present invention converts the time-of-flight which represents the relative distance between the obstacle and the ultrasonic transceiver to a digital control signal for controlling the intensity or color of a lighting system, therefore a low-cost and reliable remote control device for the lighting system is provided.
Besides, an ultrasonic device when designing its control application should be considered with directionality. The directionality of the ultrasonic device depends on its beam angle. The directionality of the ultrasonic device is better when the beam angle of the ultrasonic device is narrower. That is to say, the reflected signal detected by the ultrasonic device with narrower beam angle becomes stronger, but at the same time the detected range of the ultrasonic device becomes smaller. If the ultrasonic device is applied for displacement calculation, the ultrasonic device should be designed with better directionality. The afterward signal processing and displacement calculation benefit from stronger reflected signal detected by the ultrasonic device. On the contrary, the directionality of the ultrasonic device is worse when the beam angle of the ultrasonic device is wider. That is to say, the reflected signal detected by the ultrasonic device with wider beam angle becomes weaker, but at the same time the detected range of the ultrasonic device becomes wider. If the ultrasonic device is applied for on/off control, the ultrasonic device can be designed with worse directionality. Therefore, the ultrasonic device with wider detected range is more suitable for on/off control.
In prior art, a horn is added to narrow the beam angle of the ultrasonic device so that the directionality of the ultrasonic device is improved. U.S. Pat. No. 3,516,384 discloses an ultrasonic device in combination with a vehicle in which ultrasonic sound is beamed in advance of the moving vehicle on a thoroughfare so that said sound may be heard by an animal ahead of the moving vehicle to induce the animal to leave the road before it is struck by the vehicle. A horn in positioned ahead of the ultrasonic device to improve the directionality of the ultrasonic device in the claimed invention. In addition, U.S. Pat. No. 5,110,403 discloses a horn having improved efficiency.
In view of the above prior art, the ultrasonic devices have both the merits of motion detection and displacement calculation. If a lighting system adopting ultrasonic devices is turned on/off based on motion detection, and the intensity and the color of the lighting system is then controlled after the lighting system is turned on, at least two ultrasonic devices are needed to accomplish the above functions. Wherein one of ultrasonic devices are applied for motion detection (i.e. controlling on/off of the lighting system) while the other ultrasonic device are applied for displacement calculation (i.e. controlling the intensity and color of the lighting system). However, this kind of configuration for the lighting system requires higher cost and the space for designing the lighting system is also limited. Therefore, a solution of improving the configuration and designing space for the lighting system adopting ultrasonic devices is the subject matter of the present invention.